This invention relates to controlling the rotational speed of a rotational output part of a fan used for cooling components of a motor vehicle. Typically, such fan is driven by a viscous friction clutch which is coupled to a driving rotational part by way of a shearing fluid whose effective fluid quantity determines the transferable torque. Such driving rotational part is typically driven, directly or indirectly, by the prime energy supply (e.g. internal combustion engine) of the vehicle.
Arrangements of this type are used, for example, for controlling the rotational speed of a fan for cooling motor vehicle components such as engines, engine fluids, and vehicle accessories. In such cases, the fan can be coupled to the vehicle engine by way of the fluid friction coupling. Alternatively, the fan can be driven by a separate electric motor, powered from the vehicle electrical system, through an electrical control system. Accurate cooling control is essential for efficiency gains related to engine compartment cooling.
Whether the fan is driven by a viscous friction coupling to the engine drive shaft, or by a separately powered electric motor, activation of the fan, and control of fan speed, are controlled by a control system. Improved such control systems are the subject of this invention. Thus, while the remainder of this disclosure is directed to controlling a viscous friction coupling, or clutch, which drives the cooling fan, the same inventive parameters can as well be applied to a fan which is driven by an electric motor separately powered from the vehicle electrical system and not directly connected to the mechanical power developed by the prime energy source which serves as the general power source for the vehicle.
A wide range of applied cooling capacities are required by motor vehicles, depending on the conditions in which the vehicles are operated, as well as the loads being placed on a vehicle, on the engine, on engine components, and on vehicle accessories. The degree of cooling required during engine operation varies from a low level under light load conditions in cool weather, to a high level under heavy load conditions in hot and humid weather.
The fan is used to provide cooling air flow for diverse engine-related and vehicle-related media, such as engine coolant, charge air, engine oil, transmission oil, and retarder oil. The fan is also used, as required, for cooling refrigerant of an air conditioning system.
The fan is typically positioned rearwardly, in the vehicle, of such cooling devices as a coolant radiator, an air conditioner heat exchanger/condenser, a transmission oil cooler, and the like, which are typically positioned behind the grill at the front of the vehicle. Thus, operation of the fan draws ambient cooling air under a low negative pressure through such forwardly-disposed devices, thereby assisting in transfer of heat from such devices to the ambient air.
Correspondingly, the fan is typically placed frontwardly, in the vehicle, of the vehicle engine or other main heat source, whereby the air drawn through e.g. the one or more forwardly-disposed heat exchangers, radiators, is expelled from the fan and blown under a small positive pressure toward the rear of the vehicle and over the engine block and other heat-producing components in the engine compartment, thus to dissipate heat to the so-expelled ambient air.
The operation of a single fan is thus used to provide cooling air, and corresponding heat dissipation, to a substantial number of heat sources, each of which has a different requirement for heat dissipation. All such heat sources can tolerate operating at conditions wherein an external surface of the heat source is at ambient temperature. All such heat sources have high temperature limits which cannot safely be exceeded. Some such heat sources have optimum temperatures or temperature ranges whereat efficiency is improved or optimized.
Historically, the fan was run at such cooling capacity that all cooling needs were intentionally exceeded, and whereby no further control of the fan was exercised, and no monitoring of temperatures was used in fan control. However, such intentional overcooling, in combination with the lack of use of temperatures in controlling fan speed, can result in reduced efficiencies in some heat sources, and undetected overheating of one or more such heat sources.
More recently, conventional practice is that various parameters representing existing engine and vehicle e.g. heat-related conditions are fed into a controller which processes the various inputs, determines a desired fan speed, and sends a signal corresponding to the desired fan speed, to the viscous clutch or electric motor, whichever is running the fan. Referring to the viscous clutch embodiments, the signal is received by an actuator on the viscous clutch, which actuates the clutch to adjust the effective amount of shearing which takes place in the clutch, thereby to adjust the speed of rotation of the fan. When more cooling is needed, the speed of the fan is increased. When less cooling is needed, the speed of the fan is reduced.
For this purpose, the viscous clutch has a storage chamber and a working chamber which encloses a rotational driving part in the form of a driven coupling disk and between which an inflow path and a return flow path, respectively, are provided for shearing fluid circulation. Such circulation is caused by a circulation pump which pumps the shearing fluid from the working chamber into the storage chamber. The valve, which can be actuated by e.g. a solenoid, controls the shearing fluid circulation and thus the quantity of shearing fluid which is, in each case, situated in the working chamber which is available as the effective fluid quantity for the transmission of torque.
Friction fluid couplings with timed electric driving of an adjusting unit for the variable adjusting of the effective shearing fluid quantity are disclosed in EP 0 009 415 B1.
U.S. Pat. No. 4,828,088 Mohan et al, which is herein incorporated by reference in its entirety, teaches sensing coolant temperature and adjusting fan speed according to the sensed coolant temperature.
U.S. Pat. No. 5,584,371 Kelledes et al, which is herein incorporated by reference in its entirety, teaches sensing engine speed, coolant temperature, nominal engine temperature, fan speed, and whether the air conditioner is on or off, and adjusting fan speed accordingly.
U.S. Pat. No. 5,947,247 Cummings III, which is herein incorporated by reference in its entirety, teaches a continuously variable fan output speed, and electric control circuitry which continues to alter the signal to the control valve until the sensed speed matches the desired speed. The controller is provided with a series of processing algorithms which respond to the signals from the sensors which sense the sensed conditions. The algorithms provide response signals appropriate to the sensed conditions, and thereby determine the desired fan speed. Named sensed parameters are fan drive oil temperature, engine coolant temperature, charge air temperature, hydraulic oil temperature, and engine speed.
U.S. Pat. No. 6,079,536 Hummel et al teach a temperature stage analysis in the controller feeding a rotational stage speed controller, and multiple speed demand units in parallel, wherein the signal with the highest rotational speed demand, including incorporation of correction adjusting signals, is selected for implementation of fan speed. The parameters sensed are retarder temperature, charge air temperature, engine coolant temperature, air conditioner on or off, engine speed, engine torque, momentary speed of the coupling disc of the friction clutch, actual fan speed, fan drive speed, desired fan speed, and engine brake demand. The various demand signals are fed in parallel to a maximum value selection controller, along with certain correction signals, thereby to arrive at a desired fan speed, which is then transmitted to an actuator which implements such fan speed at the fan.
The purpose of such controlling of fan speed is to ensure that adequate cooling is provided while limiting the amount of energy consumed in the process of providing such cooling.
And while certain advances have been made, in certain instances, the cooling protocols and algorithms of the known art provide more cooling than is required or desired, and in other instances, such protocols and algorithms of the known art provide less cooling than is required, or desired.
It is an object of the invention to further refine the art of control of vehicle engine cooling fans by controlling the fan speed using alternative and additional control parameters.
More specifically, it is an object of the invention to provide a control sequence which applies a temporarily higher coolant temperature when the vehicle transmission is in Park while a power-take-off unit (PTO) is in operation.
Also more specifically, it is an object of the invention to provide a control sequence which engages the fan at maximum driven speed when the vehicle throttle command is zero and engine rotational speed exceeds a predetermined speed.
It is yet another specific object to provide for a minimum fan speed when the vehicle air conditioning system is in operation.
Method and apparatus for controlling rotational speed of a cooling fan in the engine compartment of a mobile vehicle. The purpose of the cooling fan is to dissipate heat generated by operation of the vehicle. A fan control unit receives inputs from a number of sensors and uses such sensor inputs in determining a fan speed which meets various requirements of the vehicle cooling needs while limiting the amount of energy consumed by the fan, and in some instances, improving efficiency of one or more of the operating parameters of the vehicle.
In a first family of embodiments, the invention comprehends a method of controlling rotational speed of a cooling fan positioned to provide primary cooling to at least one of an engine, vehicular fluids, or vehicular accessories in a motor vehicle having a primary energy source, and a transmission. The method comprises supplying sensor data from multiple sensors sensing heat-related information, to a fan control unit. The sensor data include at least one of (i) power-take-off activation and whether the transmission is in park, (ii) throttle command and engine speed, and (iii) fan speed and when an air conditioning system of the vehicle is activated. The method further includes receiving the sensor data into the fan control unit and processing the sensor data according to one or more pre-programmed algorithms, and thereby determining minimum fan speed demands according to respective individual data inputs as well as according to data representing selected sets of data inputs from respective different data sensors and thereby developing a set of minimum fan speed determinations; selecting from the set of most current fan speed determinations, that fan speed determination which represents the greatest fan speed; and sending, to an actuator on the fan, a fan actuation signal corresponding to the selected fan speed thereby to activate control of the fan to the selected fan speed. The method yet further comprises at least one of, (iv) when the power-take-off is activated and the transmission is in park, controlling the fan speed according to an alternate coolant temperature table, (v) when the throttle command is zero and rotational speed of the primary energy source is above a predetermined maximum threshold, setting the zero-throttle fan speed determination at maximum and including such zero-throttle fan speed determination in the current set of minimum fan speed determinations, and (vi) when the air conditioning system of the vehicle is activated, setting the air-conditioner-on fan speed at a predetermined minimum speed and including such air-conditioner-on fan speed determination in the current set of minimum fan speed determinations.
In preferred embodiments, the method includes holding the most recent set of determinations of minimum fan speeds in a memory device and thereby developing a set of minimum fan speeds representing the most current fan speed determinations.
In preferred embodiments, the primary energy source comprises an internal combustion engine and the fan is disposed between the coolant radiator and the engine, such that the fan draws ambient air from in front of the engine and blows the air rearwardly about the engine.
Further to preferred embodiments, the fan comprises a viscous clutch fan, and the method includes sending the fan actuation signal to an actuator controlling actuation of a viscous clutch associated with the fan.
The method preferably includes, when the power-take-off is activated and the transmission is in park, controlling the fan speed according to a higher coolant temperature table than when the transmission is in a gear designed to cause movement of the vehicle.
The method also preferably includes, when the throttle command is zero, setting the fan speed at maximum when engine rotational speed is at least 1800 rpm, preferably at least 2000 rpm, more preferably at least 2400 rpm.
The method further preferably includes, when the throttle command is zero and rotational speed of the engine is above 2200 rpm, setting the fan speed at maximum.
The method further preferably includes, when vehicle speed is in excess of 50 km/hr and throttle command is low, setting the fan speed at maximum.
In some embodiments, when the air conditioning system of the vehicle is activated and the engine speed is insufficient to drive the fan at the predetermined minimum speed, which is preferably about 1200 rpm, employing an engine management system to increase the throttle setting sufficient to provide the predetermined minimum fan speed at the maximum fan speed setting.
In a second family of embodiments, the invention comprehends a control system for use in a vehicle having an internal combustion engine and a transmission, the engine having a primary cooling fan having a maximum fan speed. The control system comprises an electronic fan control unit controlling speed of rotation of the fan at speeds at and less than the maximum fan speed; a communications link connecting the electronic fan control unit to the primary cooling fan and adapted to communicate control signals from the electronic fan control unit to the primary cooling fan; and a plurality of sensors, supplying sensor data to the electronic fan control unit and thereby providing heat-related information to the fan control unit. The sensors include at least one of (i) a power-take-off sensor sensing power-take-off activation and a transmission sensor sensing whether the transmission is in park, (ii) a throttle sensor sensing throttle command and an engine speed sensor sensing engine speed, and (iii) a fan speed sensor sensing fan speed and an air conditioning sensor sensing when an air conditioning system of the vehicle is activated.
In some embodiments, the plurality of sensors comprises a power-take-off sensor and a transmission sensor, both supplying sensor data to the electronic fan control unit.
In some embodiments, the plurality of sensors comprises a throttle sensor and an engine speed sensor, both supplying sensor data to the electronic fan control unit.
In some embodiments, the plurality of sensors comprises a fan speed sensor and an air conditioning system sensor, both supplying sensor data to the electronic fan control unit.
In preferred embodiments, the primary cooling fan comprises a viscous clutch fan drive mechanism.
Preferred implementations of the invention are embodied in off-road agricultural crop-manipulation or soil-manipulation vehicles, such as tractors and combines, incorporating control systems of the invention.
Preferred implementations of the invention are further embodied in over-the-road vehicles, such as trucks and buses.